Killing X
First, Hit
Ctrl+Alt+F1.Then Login again
So enter your Username & Pass.And Kill the Display Manager.
sudo service lightdm stop
Or:
sudo service gdm stop
But if you have a Custom display manager then look for the command to Stop it…
Finally, Go to Runlevel 3
With:sudo init 3
To test you are on Ubuntu Server Mode issue:
who -r